In the complex society that we are living in, there are numerous occasions where individuals have to authenticate themselves by means other than personal recognition. Until recently, a common approach to this has been the issuance of personal identification cards which range in complexity depending on the purpose for which they are to be used. For situations that are deemed only of secondary importance, the cards may merely contain the individual's name, signature and an identification number. Here, the presentation of the card will be proof enough of the user's identity if the card signature matches that of the user's as taken at the time of use. For situations that require a more positive identification, such cards are also provided with the individual's photograph like in the case for driver's licenses and passports.
Unfortunately, these identification instruments have become the common victims of illegal falsification and duplication. The rampant credit card fraud of recent years has certainly accentuated the inadequacy of using such personal instruments to authenticate oneself in many instances. To this end when bank-issued ATM cards were finally accepted and used by the American public in large numbers in the middle 1980's, a new identification means was introduced in what is now called the PIN number or Personal Identification Number which takes the form of an easily-memorable 4-digit decimal number.
Even though superior ways and methods exist for use in identifying or authenticating an individual, particularly those that use one's natural body codes such as faces, fingerprints, retina patterns, irises and voice prints, they have only been deployed to date in highly special circumstances where the absolute security of one's identity warrants the additional complexity. Indeed, the use of fingerprints to identify unique individuals has been around for well over a hundred years. Both “rolled” fingerprint and “flatly placed” fingerprint inked impressions are commonly used and the identification can be classified as “passive” because the individual is not required to perform any finger motions during the subsequent process of identification. As is well-known, in collecting the so-called “rolled” fingerprint impressions, an individual's inked thumb or one of other fingers is rotated from one side of the nail to the other so that the entire pattern area can be printed on paper. Characteristic features or patterns of fingerprints such as “arches”, “loops: and “whorls” (referred to as “keys”) are routinely employed by fingerprint-identifying technicians to define the fingerprint patterns for easier comparison and identification of them. The so-called Henry classification is often used to determine if two prints are the same even though this system requires a skilled expert to compare the individual characteristics of the prints.
Ample prior art can be found in fingerprint detection apparatus and methodology of using fingerprints for personal authentication and identification. A list of earlier issued U.S. patents relating to the prior art has been presented in the earlier filed applications identified above in the Cross-Reference to Related Applications, and reference to such patents will not be repeated again herein.
There is hardly any doubt that the prior inventions summarized above made significant progress towards simplifying the overall mechanics for the acquisition, classification, comparison and analysis of fingerprints. They have also removed in most cases the subjectivity and ambiguity in the employment of the well-known Henry classification system to determine if two prints is matched. However, there are still many shortcomings today in the use of full fingerprints to identify and authenticate individuals. These shortcomings are briefly discussed as follows.
First of all, there is potentially a privacy issue looming when one is required to use one's full fingerprint in the future as a way to authenticate oneself, especially when the level of security required does not justify the use of such a unique and private identification apparatus. Rightly so, many people today still consider their fingerprints as very private and the mandatory requirement for their use in order to verify themselves in their everyday life is considered as an outright privacy invasion. Imagine starting from a certain date onwards, one is required to identify oneself everywhere one goes and everything that one does with one's fingerprint. Since one's full fingerprint is uniquely and absolutely traceable to oneself, and furthermore, it is kept by Big Brother and many establishments such as banks, hotels, company where one works etc., it is likened to letting somebody know every move that one makes for the rest of one's life. Worse still, when this is coupled with the fact that one's fingerprints are easily “skimmed” and falsified, such as with the use of the so-called “gummy fingers” technique, one's concern about privacy and fraud would no doubt turn into a nightmare. It is commonplace for individuals to casually leave behind their fingerprints in performing their normal daily activities such as the handling of glasses and utensils when eating in restaurants, touching objects of all kinds in public places etc. without ever heeding the potentially serious consequences. The fact is that it is actually quite easy for someone to lift an individual's fingerprints left behind in such instances. This will be likened to the stealing of one's most private personal identity in order to commit all kinds of fraud against the individual without that individual even knowing about it until it is too late. Many people argue that such fingerprint skimming and falsification for committing fraud episodes will never happen. The same was said once to the magnetic stripe credit card fraud in the early 1960's when only a handful of cards were issued. But when the deployment of fingerprints becomes as popular and numerous as magnetic stripe credit cards of today, such skimming and falsification fraud is simply inevitable and the situation is likely to be even worse than magnetic stripe card fraud of today because once one's fingerprint is compromised, there is absolutely no way to rectify it.
Almost all fingerprint analysis methodology developed and in use today relies upon the number of minutiae, their classifications and their spatial coordinates of any two fingerprints as the basis for their “match” or “no match” decisions. Such a methodology requires the use of a full and a reasonably good fingerprint image resolution (>200 dpi) for analysis. Thus, full fingerprint readers used for authentication of individuals today all generate one's full fingerprint image to start whether the sensor is a silicon IC imager (imaging CCD), optical scanner, capacitance array or thermal-detector array imagers. Except for some very expensive optical scanners, all the other fingerprint readers are hardly robust enough to withstand the heavy use and rough handling by the user public, especially in unsupervised situations when there is nobody around to safeguard the proper use and prevent the mishandling of these devices. Accordingly, for fingerprint readers of today, they are either too expensive for wide use applications, or they are simply not robust enough to be practically viable. Common abuses such as ESD (electrostatic discharge), scratching and/or excessive use of pressure, water on the device surface due to condensation of moisture in the air or the use of wet, oily or dirty fingers, all are reasons why these devices have routinely failed lately during extensive field trials, particularly in unsupervised situations.
Thus, despite the deployment of enormous amounts of manpower and resources over the years to the development of fingerprint readers, both in fingerprint analysis software and image generation hardware, there is still a long-felt and urgent need for the availability of a low-cost and robust fingerprint reader for no supervision situation deployments. Furthermore, in order to alleviate the impact of privacy issues and the threat of “gummy fingers” skimming and falsification of one's fingerprints for the purpose of committing fraud, a new methodology utilizing only a subset that cannot be traced back to the full fingerprint, and not the full fingerprint itself, is needed that will eliminate both of these additional potential shortcomings for full fingerprint readers in use today.